VS Is Bottleneck
The VS Is Bottleneck metric represents the percentage of time that the vertex shader (VS) stage is a bottleneck. This is the percent of time the VS unit is stalling the Vertex Fetch (VF, upstream unit) and starving the Hull Shader/Geometry Shader (HS/GS, downstream unit).
If VS Is Bottleneck is 90, then the vertex shader stage is a bottleneck (stalling both the upstream and downstream units) 90% of the time.
Vertex processing depends on the amount of work performed per vertex. Try simplifying the vertex shader or reducing the number of vertices. In the Intel® GPA Frame Analyzer, try editing the vertex shader in the Shaders tab. For example, try a simpler vertex shader that does less work, or has fewer instructions.